Tray packing-shrink wrapping packaging machines are well known in the prior art.
FIG. 1 shows in schematic fashion the function provided by such packaging machines. In FIG. 1, a bulk product infeed to be processed is indicated generally at 10 and typically includes cylindrically shaped article 12 usually standing on end, but otherwise generally randomly oriented. One example of such articles would be soft drink beverage cans, although other products such as jars, bottles, or other containers are typical, too. In the conventional prior art tray packing-shrink wrapping operation, bulk product infeed at 10 moves along a conveyor path indicated in succession by arrows 14, 16, 18, 20, and 22 to a number of workstation areas for processing as hereinafter described. At 24, the incoming bulk articles are laned into single file in parallel rows 26, 28, 30 and 32 as shown with individual articles such as for example 34, 36, and 38 in row 32 and generally touching each other along said rows such as 32 under the influence of normal line feed pressure exerted along the direction of arrow 16 by a routine line pressure source such as an infeed conveyor (not shown in FIG. 1). It is understood that the number of rows were chosen as being four for illustration purposes only, as other numbers of rows can be used as well. Laning is typically accomplished by introducing the bulk infeed to a plurality of spaced apart, parallel guide rails forming parallel channels therebetween.
After being laned into rows at 24, the articles are next formed into arrays or groups such as group 40 and group 42 of sixteen articles each in a matrix such as for example the 4.times.4 matrix at the grouping area 44. The two groups 40 and 42 are for illustration only, as it is understood that a continuous number of successive groups are generated.
After grouping at 44, the groups proceed in succession to area 46 where each group is loaded into its own tray 48. The tray loading operation typically includes loading the group onto a tray blank, which blank is folded, glued, and compressed to form tray 48.
After tray loading at 48, the tray loaded article group is wrapped in a generally rectangular sheet 50 of wrapping material at 52, such as for example 3 mil polyethylene film. Wrapping is usually accomplished by positioning what will later be referred to as the leading edge 54 of sheet 50 under tray 49 as shown near the leading edge 56 of tray 49, using a wrap rod (not shown in FIG. 1) to wrap sheet 50 around tray loaded articles 58 by pulling the trailing edge 60 of sheet 50 around articles 58 and positioning sheet trailing edge 60 to be tucked under the sheet leading edge 54 indicated at 62 as tray 49 moves forward. The ends of the wrapped package 58 are generally left open in a cross-machine or widthwise direction indicated by arrow 64.
After wrapping at 52, the package 58 is subjected to heating such as in a heat or shrink tunnel (not shown in FIG. 1) to shrink the polyethylene film snugly about the package 58 as indicated at 66, forming what is referred to as "bulls eyes" in either end such as at 68.
Machines for accomplishing such tray packing-shrink wrapping operations generally are well known. However, in actual practice it may become desirable to tray pack-shrink wrap a wide variety of articles having differing sizes, such as heights and diameters, from batch to batch. For example, the operator of a tray packer-shrink wrapper may wish to process a batch of cans such as 211.times.4 cans for an hour or two, then switch over to a batch of larger cans such as the size 300.times.407 for a subsequent time period, and so on for other differently sized batches.
When changeover from processing batches of one product size to another is required, prior art tray packing shrink wrapping machines can require substantial, tedious, and time consuming manual adjustments and changeout of physical parts. For example, one known machine uses a pair of servomotors controlled by microprocessor-based control modules to operate the grouper section 44 and also another servomotor to operate a film feed section at 52, where the polyethylene sheet is fed to the wrapping operation. However, changeover from one product or article size to another is still relatively time consuming. For example, in this prior art machine the grouping system consists of a sliding mechanism to which the articles to be grouped are fed. As the sliding mechanism oscillates backwards and forwards, a collating comb is alternately lowered and raised so that the comb alternately releases a group and then holds back the main product infeed. The raising and lowering of the comb is controlled by a programmable controller, while the movement of the sliding mechanism is controlled by a servomotor to follow a predetermined acceleration/deceleration curve whose form depends upon the system format. However, if there is a changeover involving a change of product diameter, then the comb will need to be changed as well as adjusting the spacing between guide rails to match the new comb. This can be a cumbersome and tedious procedure. Also, the film wrapping rod for carrying the film around the package as shown at 52 receives the film sheet under control of the film feed servomotor, but the rod follows a path that must be manually set by means of a handwheel to suit differing products heights. This manual operation can also introduce inefficiencies.